Electric motor lubrication

I have an old (1947±) LeBlonde Regal lathe. The huge motor (G.E. probably
only 2 hp) has grease fittings on each end (motor housing). Do I really use
grease? Do I replace the zerks with cups and add oil? Or do I modify my
grease gun to use oil?
All advise appreciated.
Ivan Vegvary
Reply to
Ivan Vegvary
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Hi Ivan, I used to run an early '60s Devlieg jig mill at work with a huge motor that also had grease fittings at each end. We did (and still do) use grease in it. Ours has plugs on the opposite side of the housing from the zerks that need to be removed before new grease is added or you'll blow out the seals and pump the motor full of grease. We just pull out the plugs and pump in new grease thru the zerk till the new grease starts coming out of the plug hole and replace the plugs. Paul
Reply to
Paul
I have an even older Wagner 7.5 HP motor with grease fittings on each end. Grease is a way to keep something oiled without having to tend to it very often. Think of grease as it was originally . . . oil absorbed into soap flakes.
Bob Swinney
Hi Ivan, I used to run an early '60s Devlieg jig mill at work with a huge motor that also had grease fittings at each end. We did (and still do) use grease in it. Ours has plugs on the opposite side of the housing from the zerks that need to be removed before new grease is added or you'll blow out the seals and pump the motor full of grease. We just pull out the plugs and pump in new grease thru the zerk till the new grease starts coming out of the plug hole and replace the plugs. Paul
Reply to
Robert Swinney
Over lubrication is the primary cause of premature bearing failure. Check out lube recommendations on the bearing or grease manufacturers web site. Depending on the capacity of your grease gun usually a couple of shots periodically will suffice.
Reply to
Tom
Interesting. I never heard that before. I had always assumed that the first grease was derived from animal fat.
Best wishes,
Chris
Reply to
Christopher Tidy
Is that true? What damage does it do to the bearings? The worst I've seen is for the excess grease to squirt out and make a mess.
Best wishes,
Chris
Reply to
Christopher Tidy
Grease is a great insulator - the rollers will push it out of their path forming a wall which prevents it from dissipating the heat.
Reply to
Tom
Good point, Grant. I'd overlooked that.
Does anyone know of a book which describes the process of making grease from oil and soap flakes? I'd be interested to read about it.
Best wishes,
Chris
Reply to
Christopher Tidy
The "soap" isn't necessarily something you would wash with. Lithium is one "soap" used. So is Sodium, and Barium, as well as Calcium and aluminum.
All the above are considered "soap" type greases. I don't know of any grease in common use made from Lye soap (or Ivory Snow) ** Posted from
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That depends on the size of the bearing. let's say for a 1/4" ID bearing, the balls run at approximately a 1/2" diameter, and get the SFM for that at 10,000 RPM as a starting point:
1309 SFM
Now -- let's take the shaft diameter up to say 2", and say perhaps 2-1/2" for the diameter of the bearing ball's path:
5208 SFM
And a really serious electric motor with a 6" shaft (you can guess the horsepower rating if you wish), and probably 8" diameter bearing ball path:
20,943 SFM
So -- at what speed does the grease migration start to become a problem?
Assuming the 1039 SFM as the top acceptable one with the 1/4" shaft, we get 625 RPM for the maximum speed for the 6" shaft.
And how big *do* electric motor shafts get? (Of course, the larger ones do run slower to keep from self-disassembly. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
I don't think thermal conduction is the culprit. I am pretty sure that the friction from churning the higher viscosity lubricant raises the temperature. It is an effect not commonly thought of but you can get an idea by running a power paint stirrer in thick paint. Essentially all of the power it takes to spin the stirrer is converted to heat. I had a "bush-hog" gearbox overheat and ruin the seals because I had put in oil which was too thick.
Don Young
Reply to
Don Young
I'm thinking a few thousand horsepower for a 6" diameter shaft at 625 rpm, but that's just a guess.
I thought the issue Tom was talking about was the thermal insulating effect of a thick grease barrier?
Well, I've seen alternators with 12" diameter shafts at a place where I had a summer job once. But they had plain bearings. Hydrostatic when starting, hydrodynamic when up to speed. Rumour has it than when the oil pump is switched on, you can rotate a 90-ton rotor in those bearings by hand. That's what I was told anyway.
Perhaps your reasoning explains why they don't use roller bearings in those huge alternators, as they do 3,000 rpm. I just remember being told that rolling element bearings didn't survive under those conditions.
I've also seen a ship with a half metre diameter propellor shaft (apparently solid too).
Best wishes,
Chris
Reply to
Christopher Tidy
I've sometimes seen two maximum speeds quoted on bearing data sheets: a lower speed for grease lubrication and a higher speed for oil lubrication. I guess the advantage of oil is that it can circulate and carry the heat away, so it doesn't have to rely heavily on thermal conduction.
Best wishes,
Chris
Reply to
Christopher Tidy
You're correct. The bearing has to "work harder" and the heat has nowhere to go. Speeds son't have to be all that great.
Reply to
Tom

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